Optical couplers, taps, and isolators are some of the most ubiquitous of all passive optical components found in most optical communication systems. One use of optical couplers is in the field of optical fiber amplifiers that require both a communication signal and a pump signal to be coupled into the amplifier. Optical taps are often used to remove a portion of a signal for monitoring or, more commonly to divert a portion a signal to different optical circuitry and components. Optical isolators are generally used to allow signals to propagate in a forward direction but not in a backward direction. These isolators are often used prevent unwanted back reflections from being transmitted back to a signal's source. Commercially available optical fiber amplifiers usually include a tap, an isolator and a wavelength division multiplexer at an input side of the amplifier; the output side of the amplifer usually includes two taps and an isolator. Most often, intermediate the input and output sides of the amplifier is a rare earth doped amplifying optical fiber. Unfortunately these components are provided as discrete components which are bulky and have an associated signal power loss. Therefore, there is a need to integrated these functions into a single device.
An isolated optical coupler is disclosed in U.S. Pat. No. 5,082,343 in the name of Coult et al. issued Jan. 21, 1992. The coupler described in the patent is comprised of a pair of lenses having a wavelength selective device and an isolator disposed therebetween. Although the device integrates two components required in an optical fiber amplifier and appears to perform its intended function of coupling a pump signal to an optical communication signal, there remains a need for a small, compact, integrated optical isolating device that can integrate all the required components in an optical fiber amplifier; that is, having a port for providing a pump signal and having an additional port for tapping some of the input optical signal and having different kinds of tapping functions on a plurality of output ports. For example, in many instances, where a pump signal is not required for amplification, there exists a need for an isolating device that will provide a port for tapping some of an input signal, and another port for monitoring unwanted back reflections. It is an object of this invention to provide such a device. This and other functionality can be provided by the invention described hereafter.